Identification

• Citrus is susceptible to alternaria rot disease caused by Alternaria citri. The disease is more common on lemons and navel oranges. The fungal spores are carried to the fruit with wind or water and enter fruit from the button end.
  
  

Damage

• Infected fruit starts to change color early. Initial symptoms include the presence of dark brown or black spots in the fruit navel or at the styler end. Discoloration and decay can also be seen deep into the fruit core when it is cut in half.
  
  

Control

• Keep trees in good health with adequate irrigation to prevent drought. Delay harvesting until all affected fruit has dropped as this is a necessary management procedure, according to the University of Florida Extension. Apply the fungicide imazalil or 2, 4-D on harvested fruit as this delays possible infection of healthy fruit in storage.